forked from mirrors/gecko-dev
65 lines
2.1 KiB
Python
65 lines
2.1 KiB
Python
from typing import Any, List
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from .ast import BaseNode, Node
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class Visitor:
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'''Read-only visitor pattern.
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Subclass this to gather information from an AST.
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To generally define which nodes not to descend in to, overload
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`generic_visit`.
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To handle specific node types, add methods like `visit_Pattern`.
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If you want to still descend into the children of the node, call
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`generic_visit` of the superclass.
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'''
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def visit(self, node: Any) -> None:
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if isinstance(node, list):
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for child in node:
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self.visit(child)
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return
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if not isinstance(node, BaseNode):
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return
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nodename = type(node).__name__
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visit = getattr(self, f'visit_{nodename}', self.generic_visit)
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visit(node)
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def generic_visit(self, node: BaseNode) -> None:
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for propvalue in vars(node).values():
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self.visit(propvalue)
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class Transformer(Visitor):
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'''In-place AST Transformer pattern.
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Subclass this to create an in-place modified variant
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of the given AST.
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If you need to keep the original AST around, pass
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a `node.clone()` to the transformer.
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'''
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def visit(self, node: Any) -> Any:
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if not isinstance(node, BaseNode):
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return node
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nodename = type(node).__name__
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visit = getattr(self, f'visit_{nodename}', self.generic_visit)
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return visit(node)
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def generic_visit(self, node: Node) -> Node: # type: ignore
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for propname, propvalue in vars(node).items():
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if isinstance(propvalue, list):
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new_vals: List[Any] = []
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for child in propvalue:
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new_val = self.visit(child)
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if new_val is not None:
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new_vals.append(new_val)
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# in-place manipulation
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propvalue[:] = new_vals
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elif isinstance(propvalue, BaseNode):
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new_val = self.visit(propvalue)
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if new_val is None:
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delattr(node, propname)
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else:
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setattr(node, propname, new_val)
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return node
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